Put a person one in front of another and look at the feet. You will find that with a beginner there is more of a tendency to go to the ball of the foot and not the heel. Was it Richard Geyer, or was it the big guy that did just that. I can't see any possible reaon why one minute should not be used to explain and to demonstrate the correct and the incorrect way of doing that very first step. I would say be sure that you get the heel on the floor and not the ball of the foot on the floor and then lower imediately at the end of the step. Wouldn't that be good teaching. And if you ever go for a teaching examination this had better be your explanation if asked to explain

"Put a person one in front of another and look at the feet. You will find that with a beginner there is more of a tendency to go to the ball of the foot and not the heel."

Which is why you have to get them moving NATURALLY again. What you describe is an un-natural movement prompted by initial exposure to the problem of having a partner; they have to get over that.

"I can't see any possible reaon why one minute should not be used to explain and to demonstrate the correct and the incorrect way of doing that very first step."

Perhaps becuase what is demonstrated as a purposefull heel lead is almost certainly INCORRECT. It ends up being overexaggerated and very awkward and unnatural. Simply stress natural movement, and they will start doing what advanced dancers do, skipping right over all that overemphasized silliness of those who think (incorrectly) that they know what the proper footwork is. A good heal lead is really a rather subtle thing!

A good heel lead is a subtle thing. In that case should it be ignored.